1. Field of the Invention
The present invention relates to a focus detection device suitable for a focus detection apparatus of a camera.
2. Description of the Related Art
A conventional phase difference CCD focus detection device, which is provided for an AF single-lens reflex camera, includes line sensors and monitor sensors in conformity with a photographic optical system and focus detection areas.
A focus detection device using a conventional CCD focus detection device outputs an integration termination signal when the integration is terminated for all the monitor sensors. Therefore, the way to detect integration time (light-receiving time) required for the monitor signal to reach an integration termination value for all the monitor sensors is based on integration information obtained by communication with the CCD focus detection device.
In the case where the integration information is obtained by the communication, however, the amount of time required for communication is larger than the integration time when a photographic object has high brightness and the light-receiving time is short. As a result of such long communication time, error in the integration time is increased.